There has already been plenty of discussion here about how our air filter failed (either a bystander in whatever caused the overheating, or maybe even the cause... still unknown, may never be known) - but now that our engine and engine bay are fully disassembled, I am looking for ideas of what new air filtration system to put back in its place.

About half the 4106's I've seen at various bus rallies still have the old stock oil bath filters.

But the rest (like ours) have had the oil baths removed and replaced with something else... I'd love this thread to be focused on the various "something else" options that GM 4106 owners have come up with.

Farr EcoLite C-62891-1 U -- Was on our bus when we bought it.Wix 46891 -- Second filter, 1 year / 10k miles of use.Baldwin PA2721 -- Third filter. Ingested by the engine after 4,062 miles, less than a year's use.

Where do you have it mounted? -- The filter canister is mounted directly above the engine air horn, and the intake is connected to the old bus air intake box that sucks in from the passenger side back corner of the bus. The air filter is tucked up and out of the way such that you can't really even see it when the engine rear door is open.

Have any pictures? -- Attached.

Anything you would do differently if you were to do it again? -- Doing it all again right now, and looking for advice and examples of better installations. The old large canisters were extremely difficult to change because of how tight the space was to fit up above the engine, and it was difficult to get the very short hose attached to connect back up to the air intake box. We'd also like to go to a 1200cfm or larger capacity.

I had a 4104 with only three filters, but basically the same setup. They could be messy to service but inexpensive and simple as well as reliable.Most folks that I know of, who replaced the oil bath with paper, retained the hardware and used 3 (or 4) paper filters in their place. That takes some effort to find the right elements and to fabricate the mounts necessary. They are well documented in various places on the boards.

If you still have the hardware, that is what I would do; either return to oil bath or use four paper elements.

I decided to retain the oil bath filters on my 4104 because I did a considerable amount on low speed driving on dirt roads and I think they are a better filter for that application. At that time (late 80's) a lot of agricultural equipment was using oil bath filters and considered them superior. I do believe that oil bath is a better filter, but in the end they are more expensive

My guess is that when you are paying $100 an hour or more for service, paper is cheaper and that is what the bus companies are concerned about.

One advantage of this is that I can easily convert it back to the oil bath (I have all of the guts and additional unmodified pan bottoms.) All of my research on this has only given conflicting answers. One says oil better for dirt, others say not so. I have yet to find a real study of the pros and cons of each set up, other than speculation with some reasoning, that on the surface seems to make sense. Hard to feel like I am doing the right thing without the science behind it. Anyone have solid proof? I will gladly put oil on if it is better, the majority seems to think it is not.

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L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaIts the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

Inside the bus in what is our electrical compartment and I believe is your closet we have a massive truck style air filter and housing. The system has hard pipe to pull air from both stock intake locations directly into the filter. The engine then draws the clean air through the floor of the compartment and into the engine bay.

I did manage to find this one photo of it from when we were building the electrical system.

I have a 4104 with a DD-671. Installed a Donaldson ABS filter housing and paper element. I went to the Donaldson website to size the air filter https://www.donaldson.com/en/engine/support/datalibrary/056798.pdfAfter considering ease of access, routing of ducting, and intake location, I put the filter in the inside left rear corner of the bus. This takes up some of our bedroom space, but best met the above criteria. Intake is 7 dia. Horizontal (side of housing) and outlet is 7 dia. Vertical (out the top). The ducting from the housing to the blower is 7 galvanized heating duct. All seams were taped with aluminum tape and then wrapped in Dynamat to seal. The duct is reduced to the 4 blower intake diameter as illustrated. Intake grill is 9 dia. With almost no obstruction of airflow.

Somewhere on my dream list is to close off the corner intakes and run a pipe up a rear inside corner to the top of the bus where I would have an intake off of a Road tractor. I have seen it done on several 4106s but I didn't save any photos of it. The assembly would be similar to the attached photo. It would greatly reduce the amount of dirt taken into the filter.

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L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaIts the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

An issue which has been touched on but may bear repeating is the location of the air filter. Could it be that the location of your filter in the engine compartment may have overheated the element to where it broke down, especially after a long climb?

Our filter assembly is the same set up. To make a long story short. We had to rebuild our engine before we ever got it home. Turned out to be the blower bearing. We where in the 100's most of the time and overheating after just 2 hours of driving. The engine gave up after 1000 miles of this. (DUH!) The air filter was fine after all of the abuse. I don't think it was the one time overheating. Just my 2 cents.

When I upgraded my 8V-71 from a non turbo 304hp to a turbocharged 375hp, the air cleaner was not sufficient for the increased CFM. I looked up the engine and CFM requirement on the Donaldson site and just so happened to find another air cleaner that flowed enough CFM's but was the same size. The air cleaner went from a 6" in and out to a 7" in and out. From a cylindrical air cleaner element to a conical element. Also, after measuring the air stack inlet, discovered that it too was too small. I cut out the side of the bus for an additional 6x9 A/C vent, and that took care of that.Considering how relatively cheap a complete new air cleaner is, I wouldn't fool with trying to convert the old oil baths to dry filters. Just get a new air cleaner of the right size and CFM. Good Luck, TomC

Keep in mind three things....how much is/are dry filter elements going to cost vs. change frequency, how much labor is it going to cost to replace element,s, if you can't do it yourself, and how easy is it going to be to obtain replacement element, out on the road? You might consider a filter reminder, or as some say they are worthless, a vacuum gage tied into air intake. Consider a truck boneyard for a replacement air filter unit;take along a measuring tape.